The following is an excerpt from the United States Copyright Office website
Can a school show a movie without obtaining permission from the copyright owner?
If the movie is for entertainment purposes, you need to get a clearance or license for its performance.
It is not necessary to obtain permission if you show the movie in the course of “face-to-face teaching activities” in a nonprofit educational institution, in a classroom or similar place devoted to instruction, if the copy of the movie being performed is a lawful copy. 17 U.S.C. § 110(1). This exemption encompasses instructional activities relating to a wide variety of subjects, but it does not include performances for recreation or entertainment purposes, even if there is cultural value or intellectual appeal.
Questions regarding this provision of the copyright law should be made to the legal counsel of the school or school system.